The objectives of this study are to examine the effect of propranolol infusions with its associated beta adrenergic blockade on uterine and umbilical blood flows, maternal and fetal mean arterial pressure and heart rate, gas and acid-base status. Pregnant Dorset sheep are operated between 120-130 days gestation. Electromagnetic flow probes and catheters are placed on and in pertinent maternal and fetal vessels allowing a chronic preparation to be obtained. After a minimum of 48 hours to allow for recovery and reestablish maternal and fetal homeostasis, the test drug is infused.